The present invention relates to a wiper motor, which has an electric motor and an output shaft for outputting motive power generated by the electric motor and swings a wiper arm attached to the output shaft.
In a rear wiper device or the like for wiping a rear window glass of a vehicle, a wiper motor having a motive power conversion mechanism for converting rotary motion of the electric motor into swinging motion of the output shaft is used to directly fix the wiper arm to the output shaft.
Such a wiper motor has a gear case comprising a case body formed into a bathtub-like shape and a cover for closing the case body, wherein a worm wheel of a worm gear mechanism for reducing the rotation of the electric motor and an output gear fixed to the output shaft are rotatably housed in the case body. A linking shaft is provided at the worm wheel away from a rotation-central axis, and an arm part serving as a motive power conversion member is rotatably connected to the linking shaft. In addition, a sector gear part meshing with the output gear is provided in the motive power conversion member, and a gear shaft which is press-fitted in an axial center of the sector gear part is rotatably supported by a swinging plate swingably supported by the output shaft. For this reason, when the electric motor operates and the worm wheel rotates, the arm part reciprocates and the sector gear part swings around the output gear, whereby the rotary motion of the worm wheel is converted into the swinging motion of the output shaft by the motive power conversion member.
In such a wiper motor, when an external force due to, for example, mischief is applied to the wiper arm or while the electric motor is operated, a load in a direction of separating these gears is generated between the output gear and the sector gear part. Then, due to the load, the gear shaft is inclined with respect to the output shaft so that the swinging plate serves as a supporting point, whereby there is such fear that mesh of the respective gears may be misaligned. Therefore, for example in the wiper motor disclosed in Japanese Patent Laid-Open Publication No. 09-224305, a resin-made slidable contact member is mounted on tip portions of the output shaft and the gear shaft and the slidable contact member slidably contacts with the cover, so that axial-directional movement of the respective shafts is restricted and looseness of the respective gears is suppressed.